The present invention relates to a magnetic storage device having a magnetizable storage disk, at least one read/write magnetic head and a track guidance system that contains a servo head rigidly connected with the magnetic head for guidance. The magnetic head is arranged on a flying body that aerodynamically glides over the moving storage disk. Electronics coupled to the servo head output keep it on the guidance track.
High density storage of information (data) on disk-shaped recording media is known according to the principle of longitudinal (horizontal) magnetization as well as the principle of perpendicular (vertical) magnetization (cf. for example "IEEE Transactions on Magnetics", Vol. MAG-16, No. 1, January 1980, pages 71 to 76 or Vol. MAG-20, No. 5, September 1984, pages 657 to 662 and 675 to 680). The read/write magnetic heads used for these kinds of magnetizations are best implemented in thin film technology on non-magnetic substrates. The distance between a magnetic head and the surface of the storage disk should be kept exceedingly small and should be below 1 .mu.m for vertical magnetization. Such small distances, however, can be practically ensured only by developing the substrate carrying the magnetic head as a flying body (a slider) which flies aerodynamically over the storage disk rotating underneath it.
To this end, the substrate on its underside facing the recording medium is best equipped with appropriate landing or flying skids (cf. for example EP-A-O 137 051). Guiding such a flying read/write magnetic head of a corresponding magnetic storage device requires a so-called track positioner and, in general, also a track holding system. Linear or angular positioners are employed for track positioning in connection with a specific servo disk. This servo disk carries a fixedly inscribed raster of guidance tracks. These tracks are read with the aid of a suitable servo head which, in rigid mechanical connection with the read/write magnetic head, ensures that the track pattern is transferred to the data surface of the actual data storage disk and can, correspondingly, be found again during the read process.
The mechanical tolerance of the drive system for the storage, servo disk and the head positioner determine the limits of this guidance technology. Any further increase of track density therefore requires, for example, further development of the drive mechanics. The expenditures required in production are, however, very high and, hence, cost-intensive. Known alternatives are additional servo measures in which the storage disk itself is drawn on for track guidance. A corresponding arrangement, referred to as an "embedded servo", reads previously fixedly written servo data before each storage block to follow up the track positioning. A variant of this technique is described, for example in "Electronics", Nov. 13, 1986, pages 81 to 83. This servo principle, however, presupposes that the cooperation of drive mechanic and head positioner is reproducable within limits of, for example, .+-.2 .mu.m. However, current development tendencies that use the principle of vertical magnetization aim for track widths in the range of 10 .mu.m or less. The servo systems must continuously track the read/write magnetic head using so-called "track locking".